1. Field of the Invention
The present invention relates to a lens barrel adapted for an optical apparatus such as a camera or the like, and more particularly to the dust-proof and drip-proof structural arrangement of a lens barrel or the like.
2. Description of Related Art
The rotating parts, such as rotary operation parts, of lens barrels are often arranged to be in a dust-proof and drip-proof structure. Generally, the dust-proof and drip-proof structure is arranged to prevent intrusion of water, dust, etc., by inserting a rubber O-ring in between a body member and a rotating member of the lens barrel.
However, such a dust-proof and drip-proof structural arrangement generates a large frictional force between the O-ring and the rotating member. The large frictional force necessitate exertion of a large force in operating the rotating member. The conventional arrangement thus has often made the rotating member difficult to operate, or has prevented effective utilization of space due to limitation imposed on the diameter of the O-ring.